Everyone is missing a crucial point with why this movie is bad. Look at all of Night's movie before the Last Airbender.
How many of those movies have fight scenes using martial arts [http://www.imdb.com/name/nm0796117/#writer1990]? As far as I can see none.
If I were going make a Kung Fu movie which the Last Airbend basically is or at least should have been, wouldn't it make sense to have a director with experience making that genre of movie on the project.
Ang Lee, Rob Minkoff, any number of other talented experienced kung fu movie directors would have been much for this movie than Mr.Shyamalan.
And trying to condense 10 hours of story, character development, and plot development from the first season of the series into 90 mins was just foolhardy.
First movie should have tried to accomplish these things alone:
1. Introduce develop and start the hero journeys of the four main characters, Aang, Zuko, Katara, Sokka.
2. Demonstrate Aang's playful nature and free spirit upbringing, Katara desire to learn waterbending, Zuko's desire for approval from his farther, and Sokka's ability as warrior.
The first movie should have ended when they reached the Northern Water Tribe after Aang and Katara start training in waterbending. This first movie should have been them going on adventures that educates the audience on everything they need to know to understand the rest of the story.
In other words it should have primarily been exposition and introduction to the main conflict of the series, that's 10 hours worth of adventures they tried to cram into 90 mins.
This movie fails on so many levels he even admits to using people who didn't know how to act because they had martial arts experience. I'm sorry but that's just ass backwards, you can train a good actor for a year to be competent in martial arts but that doesn't mean the opposite is true, which this movie proves.
And if casting was really such an issue why didn't he just age the characters a few years? It's what the David Lynch director of "Dune"1984 and John Harrison Director of "Dune" 2000 did when they need a better talent pool.
Making Aang 16 instead of 12 wouldn't have a huge impact on the story or really alienate an audience and would be an understandable if not fan supported decision. I'm willing to bet that if Uwe Bolly had made this movie it would have been better.